DE-U 72 03 658 discloses a cylinder lock which has a cylinder housing in which a cylinder core is rotatably mounted. The cylinder core has, in its central region, an axially extending key channel and guide slots which extend radially therethrough in a direction perpendicular to a longitudinal axis of the cylinder core. In each of the guide slots, two spring-loaded plate-shaped tumblers, so-called plate tumblers composed of sheet-metal punched parts, are seated therein so as to bear against one another in pairs, or axially adjacently, and so as to be alternately and radially movable. When the key is removed from the key channel, the plate tumblers radially engage in their blocking position (i.e., on account of the spring loading) into radially opposing blocking grooves which extend in the axial direction of the cylinder housing, such that the cylinder core is seated in a rotationally fixed manner in the cylinder.
The plate tumblers are of solid-frame-type design and have in each case two frame longitudinal webs and two frame transverse webs which form a substantially rectangular recess which is aligned axially with the key channel. Inwardly protruding control cams are arranged at inner edges of the frame longitudinal webs.
The appropriate flat key has a key bit or middle web which is substantially rectangular in cross section and which has two wide side surfaces and two narrow side surfaces. In each case, one groove-like recess is provided mirror-symmetrically oppositely on the wide side surfaces. The recesses extend in the longitudinal direction of the key bit and have groove walls which are aligned at right angles to the groove base, wherein the recesses are designed as control edges or control paths which interact with the correspondingly arranged control cams of the plate tumblers.
The paired arrangement makes it possible to use reversible keys which can be inserted into the key channel to actuate the closing mechanism by rotating the keys 180° about their longitudinal axis of the key bit. Here, the plate tumblers are pulled back into the interior space of the cylinder core counter to the respective spring force. On the basis of this known design, it is possible to use high quantities of different plate tumblers and thereby ensure high numbers of variations of locks. Furthermore, a shorter, more space-saving design of the closing cylinder is possible. On the other hand, a cylinder lock of said type still requires a relatively large cylinder core diameter of more than 15 mm, for example, as a result of which the spatial requirement in this respect still does not meet various needs and desires, such as those of the automobile industry.
Cylinder core diameters of less than 15 mm are possible using cylinder locks with plate tumblers which have closing cams on the inner edges of the frame transverse webs, with the control paths being formed on the narrow side surfaces of the key bit (DE-U 76 37 619). A disadvantage of such an arrangement, however, is the possibility of simple reproduction and a weakening of the key bit by means of excessively deep milled portions of the control paths, for which reason said cylinder lock type with plate tumblers is no longer common in motor vehicle doors despite its small design.
A further cylinder lock type with plate tumblers and with a particularly high level of variation diversity of the control edges and particularly high strength of the flat key is known for example from DE 27 42 165 C2. The cylinder core of the closing cylinder has plate tumblers which are alternately spring-loaded towards one another and the flat key is provided with oppositely-aligned, stepped incision paths or control paths which are open to opposite narrow sides of the flat profile and which are separated from one another by a continuous key bit or middle web of the flat profile. In said known cylinder lock type, the flat key has a Z-shaped basic profile with the middle web, and two incision paths or control paths are arranged on the inner surfaces, wherein each faces towards the opposite narrow side of the flat profile of the two Z-limbs. To be able to operate said cylinder lock type with a reversible key which facilitates use, the control paths are formed so as to be mirror-symmetrically identical to one another, though this restricts the variation diversity. Furthermore, when using the reversible key version, it is not easily possible to ensure a closing cylinder diameter of less than 15 mm.
It is an object of the invention to increase the variation diversity of a cylinder lock type known from DE 27 42 165 C2 and the like, while simultaneously permitting the use of a reversible key for this purpose. Furthermore, it is also an object to produce a closing cylinder having a diameter of less than 15 mm, yet capable of accommodating up to 8 plate tumblers, for example.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.